Ultrasonic inspection of sail joints



Feb 28. 1956 H. a VAN VALKENBURG ErAL 2,736,193

ULTRASONIC INSPECTION 0F RAIL JOINTS Filed July 2. 1953 I 2m-w1 L27 i 26j v 25 Ill 60M Y A 24 MSWI# A, 26 swsfp I GMM/#MR 2,736,193 PatentedFeb. 28, 1958 ULTRASONlC INSPECTION F RAIL IOINTS Howard E. VanValkenburg, Candlewood Isle, and Raymond E. Sansoni, Bethel, Conn.,assignors to Sperry rortilncts, Inc., Danbury, Conn., a corporation ofNew Application Italy 2, i953, Serial No. 365,632

2 Claims. (C1. 'I3-67) This invention relates to the ultrasonicinspection of rail joints. In such inspeaion, ultrasonic beams are pen'-odically transmitted in to the rail through the head thereof, and ifthere are internal defects, the beams are reilected by the retlectingmrfaces of such defect back to the transmitting point where they arecaused to opcrate suitable indicating means. A problem in connec tionwith such testing arises by reason of the fact that the rail joints areheld togethrr by mechanisms which comprise angle bars which are boltedto the rail by bolts passing through the angle bars and through boltholes in the rail ends. Obviomly the bolt holes constitute reflectingsurfaces in a manner similar to a defect, and in order that such bolthole indications shall not be received and therefore shall notcomplicate the indicated defects, it has been the practice heretofore toprovide gating means which gated out from the indicating means thepassage of the ultrasonic beams through a longitudinal strip of railjoint in which the bolt holes are located. Thus while the bolt holeswere not indicated, it was also the case that bolt hole cracks radiatingfrom the bolt holes to a length of as much as one-half inch were alsogated out, and therefore remained undetected. bolt hole cracks aredefects which it is desirable to detect, it is the principal object ofthis invention to provide a means whereby sach bolt hole cracks may bedetected while at the same time gating out the indications which wouldotherwise be caused by the bolt holes themselves.

Further objects and advantages of this invention will become apparent inthe following detailed description thereof.

In the accompanying drawings,

Fig. l s an assembly including a block wiring diagram, showing one formof this invention.

Fig. 2 is a side elevation, largely diagrammatic, of a portion of a railjoint and a graph in relation thereto.

Referring to Fig. 1 of the drawings, the invention is shown as appliedto the detection of defects in a rail joint indicated generally at I andcomprising the rail ends and 11 which are adagcd to be joined by jointbars, not shown, and fixed to the rail ends by bolts, not shown,extending through bolt holes 12 in the rai ends. For the ultrasonictesting of such rail joints there may be provided an electro-acoustictransducer 15 which may take the form of a piezo-electric element sischas a quartz crystal 16, preferably moonted so as to transmit vibrationsinto the rail ends at an angle. The electro-acoustic transducer l5 isadapted to be periodically energized by means of a synchronizet 2d whichis energized periodically from a suitable source of energy sach as60-cycle A. C., and said synchroniser periodically trips a pulsegenerator 21 to generate wave trains of relatively high frequency whichare applied to the transducer 15 which transforms the electricvibrations into trchanical vibrations and transmits such wave trains ofultrasonic vibrations into the rail through the rail head. The wavetrains travelthroughthenlfromtoptobottom, and if a reflecting surfacesuch as an internal defect D is ert- Since countered, the were trainwill be reected back to the transducer which will convert such rellectedultrasonic wave train into an electric voltage which after beingsuitably amplified by an amplier 22 may be applied to the verticalplates 23 of an oscilloscope 24 to deect the sweep 25 which is generatedbetween horizontal plat-:s 26 by a sweep generator 27 which is energizedby the synchronizer 2li in synchronism with the generated wave trains.

Referring to Pig. 2, it will be seen that when the: transmitted beamstrikes a bolt hole 12 such bolt hole will reflect the transmitted beamback to the transduc v 15 in the same manner as the defect D, and this woccur at every bolt hole throughout the rail joint regiert which isbeing tested. It is obvious therefore that the sweep 2S on theoscilloscope will show a large number of indications, similar to theindication of a defect, where in fact no defect exists. Therefore asstated in the introduction hereto, it has been customary to gate out allindications which would be caused by reflections of the wave train inthe region between the dot and dash lines 30. While this resulted ineliminating the indications of the bolt holes on the indicator, it alsoresulted in bolt hole cracks, such as indicated at 3l and which liewithin said gated-out area 30, escaping detection. It is desirable todetect such bolt hole cracks since they constitute true defects in therail joint area.

ln order that boit hole cracks of the type described above may bedetected, there is provided the following arrangement whereby instead ofgating out an entire longitudinal section 30 of the rail, there isgated-out only the bolt holes themselves while the portion of thesection 30 lying between bolt holes is rendered sensitive to de tection.

For this purpose there is provided the additional circuitry disclosed inFig. l, which comprises a bolt hole gate generator 40 adapted to beperiodically energized from synchronizer 2t) n synchronism with thepulse gen erator and sweep generator to cause said bolt hole generatorto apply a pulse to a coincidence gate circuit 4L Since only the region30 is to be rendered sensitive to detection, the bolt hole gategenerator does not start to generate a signal gate voltage untilfthetransmitted pulse has traveled down to the region 30. By this time thevoltage generated by the transmitted pulse, which is of relatively shortduration, has terminated. In order to render coincidence gate circuit 41effective it is essential that an additional pulse be received from theoutput of amplifier 22. Such a condition exists when the transmittedpulse first strikes a bolt hole 12. At this point the coincidence garecircuit 4l is rendered conductive so that further pulses from the outputof amplifier 22 can pass through the coincidence gate circuit andoperate a suitable indicator. However, it is not desired that any outputfrom amplifier 22 shall pass through gate circuit 41 until thetransducer 15, moving in the direction of the arrow A, nses thetransmitted pulses to pass the bolt hole 12. Therefore the output ofgate circuit 41 is fed into a delay gate generator 45 whose delay may be,Y adjusted to correspond to the time that it takes the transducer 1S tomove along the rail head a distance corresponding to the diameter of thebolt hole. As soon as this distance has been traversed the delay gategenerator-r 45 enables any signals from amplifier 22 passing throughcoincidence gate crcait 41 to venergize suitable indicating means.Therefore at the end of the delay the signals passing through concidencegate circuit 41 from the amplifier 22 will energize a relay 46 to closecontac 47 which closes the circuit to an indicating device which; may bea recorder 48 or a warning device 49, or bode Y as shown. The delay gategenerator 45 is timed so that ap'szevnaaV y .t

once it energizes relay 46 it will maintain the relay energized for thetime interval T (see ygraph in Fig. 2) which begins just after thetransmitted beam has passed a bolt hole and ends just before thetransmitted beam is about to strike the succeeding bolt hole. Thereforeif a bolt hole crack such as crack 31 occurs, it will reect thetransmitted beam sometime during the interval T and the indication inthe form of a signal voltage corning out of amplifier 22 will passthrough coincidence gate circuit 4l, delay gate generator 45, contacts47 of relay 46, and operate the indicating means 48, 49.

Since the time T is a function of the rate of movement of the transducer15, the delay interval of the delay gate generator 4S may be made afunction of such rate of movement, as for instance by causing themovement of the transducer IS to actuate a voltage generator 50 to applya biasing voltage to the gate generator. The voltage generator 50 may bemoved by the movement of the transducer l5, or in the case where thetransducer is mounted on a carriage the generator 50 may be driven fromthe carriage wheels.

Having described our invention, what we claim and desire to secure byLetters Patent is:

l. ln a rail flaw detector mechanism, said rails having bolt holes inthe joint areas, means for detecting cracks originating at the boltholes, said means comprising means movable relative to the rail forperiodically transmitting ultrasonic wave trains into the rail andreceiving reections from reliecting surfaces in the rail, said boltholes forming reflecting surfaces. indicating means normally 302,527,986

maintained ineffective, a bolt hole gate generator adapted to beenergized periodically in synchronism witbl'said wave train transmittingAmeans to generate a signal gate generating a signal voltage after apredetermined delay corresponding to the time that the transmitting andreceiving means travels past the bolt hole, said delayed signal gatevoltage continuing for a time corresponding to the travel oi thetransmitting and receiving means between bolt holes, and means wherebythe signal voltage from the delay gate generator renders said indicatingmeans effective.

2. A device as specified in claim l, in which means are provided forgenerating a voltage which is a function of the rate of movement of thetransmitting means, and means whereby said last-named voltage is appliedto said delay gate generator to vary the duration of the delay Vperiodinversely as the rate of movement of the trans mitting and receivingmeans.

References Cited in the file of this patent UNITED STATES PATENTS2,280,226 Firestone Apr. 2l, 1942 Carlin Oct. 31, 1950 2,646,555 Straehl....--.t July 2l, 1953

